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A047904 a(n+1) = a(n) + n (if n is odd), a(n+1) = a(n) * n (if n is even).

%I A047904 #31 Feb 19 2024 01:55:01
%S A047904 1,2,4,7,28,33,198,205,1640,1649,16490,16501,198012,198025,2772350,
%T A047904 2772365,44357840,44357857,798441426,798441445,15968828900,
%U A047904 15968828921,351314236262,351314236285,8431541670840,8431541670865,219220083442490
%N A047904 a(n+1) = a(n) + n (if n is odd), a(n+1) = a(n) * n (if n is even).
%H A047904 T. D. Noe, <a href="/A047904/b047904.txt">Table of n, a(n) for n = 1..100</a>
%t A047904 Transpose[NestList[{#[[1]]+1,If[OddQ[#[[1]]],Total[#],Times@@#]}&,{1,1},30]][[2]] (* _Harvey P. Dale_, Sep 11 2012 *)
%o A047904 (Python)
%o A047904 a=1
%o A047904 for n in range(1,33):
%o A047904     print(a, end=", ")
%o A047904     if n&1:
%o A047904         a += n
%o A047904     else:
%o A047904         a *= n
%o A047904 # _Alex Ratushnyak_, Feb 24 2013
%o A047904 (Haskell)
%o A047904 a047904 n = a047904_list !! (n-1)
%o A047904 a047904_list = 1 : zipWith uncurry
%o A047904                            (cycle [(+), (*)]) (zip a047904_list [1..])
%o A047904 -- _Reinhard Zumkeller_, Nov 13 2013, Mar 24 2013
%Y A047904 Cf. A000124, A047905, A077138.
%K A047904 nonn,easy,nice
%O A047904 1,2
%A A047904 Miklos SZABO (mike(AT)ludens.elte.hu)